This invention relates generally to tools for installing helical coil inserts into tapped holes, and, more particularly, to tools having means for adjusting the depths to which such inserts are installed.
Helical coil inserts are commonly installed into tapped holes of a workpiece such that threaded fasteners, e.g., screws, thereafter can be held more securely. The inserts are frequently installed in relatively soft materials such as aluminum, to improve the gripping of threaded fasteners made of relatively hard materials such as various steel alloys.
Helical coil inserts of this kind are usually installed by compressing them into a smaller diameter and then rotatably threading them into the tapped holes. Once installed, the inserts expand from their compressed diameters and thereby press radially outwardly against the tapped holes and are held securely in place.
Tools for installing the helical coil inserts are typically driven by an air motor and include a tubular tool body having a threaded opening extending along its axis and having means at one end for carrying an insert. A mandrel is received within the threaded opening and is rotatably advanced by the air motor into engagement with the insert. Further advancement of the mandrel forces the insert through a prewinder, which reduces the insert's diameter, and from there into a tapped hole in an adjacent workpiece.
The insertion depth of the helical coil wire insert is controlled by limiting the distance to which the mandrel can be advanced. Typically, this has been accomplished using a sleeve of a desired length which is positioned between the tubular tool body and a flange on the mandrel. In order to change the insert's installation depth, the mandrel had to be removed from the tool body and a different-length sleeve or spacer put in position around the mandrel. An exemplary tool of this kind is shown in U.S. Pat. No. 3,111,751 to Eddy.
The need to remove the mandrel from the tool body in order to adjust the insert's installation depth is unduly time consuming. This has been a particular problem when a large number of inserts have to be installed at a variety of depths.
Another approach has also been used previously, with equal difficulty. A stop collar has been used to limit the distance the mandrel could travel and thereby set the depth to which the helical coil insert could be installed. A set screw secured the collar in a selected position on the mandrel, but the collar would often slide up or down the mandrel after repeated use, because of vibrational forces and the force of the collar jamming against the tool body.
It should therefore be appreciated that there is a need for an installation tool for helical coil inserts that quickly and conveniently allows the adjustment and setting of insertion depths. In particular, there is a need for a tool that can be adjusted without having to disengage the mandrel from the tool body, without having to maintain an inventory of a number of different-length sleeves, without having to retighten a stop collar that loosens due to vibration and jamming, and without having to substantially disassemble the entire tool. The present invention fulfills this need.